flyd-group-within v0.0.3

flyd-group-within

                                     500 ms        500 ms
(S = start, E = End) Timer          S        E    S       E
                                    |        |    |       |     
upstream: (ticks represent 100ms) [-:1-2-3---:----:5-6----:-----]
groupWithin(500,stream):          [----------.------------.-----]
downstream:                                  [1,2,3]      [5,6]

install..

npm install flyd-group-within
npm install sourcevault/flyd-group-within#dist 

simple example ..

var groupWithin = require ("flyd-group-within") 

var send = flyd.stream()

setTimeout (function(){send(1)},100)
setTimeout (function(){send(2},200)
setTimeout (function(){send(3)},300)
setTimeout (function(){send(4)},1000)
setTimeout (function(){send(5)},1100)

groupWithin(500,send)
.map function (x){
   console.log(x) 
}
// [1,2,3]
// [4,5]

Why ? ..

Lower Bound Buffering

• Lets say you are sendind data to a server over HTTP.

• You kown the lower bound overhead to physically send a packet and process the date is 200 ms.

• you have a send function that can be used to send the data.

• If the send function is called every < 200ms, by definition there will be backpressure which if left unresolved will cause the recieving server to either run of memory, be unresponsive or in the worst case crash.

• A simple protective measure is to multiplex multiple send operation into a single packet minimizing the handshake overhead - it's the same principal of using trains and buses to reduce road traffic.

Any type of IO where there is an constant overhead of doing the IO itself can find this type of buffering useful. There is another option that involves grouping n send calls, however that type of design provides no garantee regarding maxmimum wait time for the buffered send to be dispatched.

setTimeout also does not give a hard garantee regarding dispatch time - you can observe it when send operations are queud in the timeout boundaries of flyd-group-within, but that is besides the point since no system that does cooperative concurrency will give you that anyway. Just make sure your callbacks in the main eventloops is not blocking or running a long loop.

GUI IO Time Slicing

Double mouse click is a good example of this application, buffer all mouse clicks in a 200ms windows, if there are 2 mouse clicks within a 200ms window, it becomes a double click, 3 mouse click becomes a triple click, so on and so on . .

I am sure it can be used in other ways that others are better cable of finding out than me, if you would like to add your usecase do not hesitate to submit a pull request.

LICENCE

Code and documentation is released under MIT Licence, see LICENSE for details.